The imperial overreach of ants

 

I can´t get the Argentine ants out of my mind, I mean, *have* they taken over...the world or something?! And right under our very noses, they did! Rather than try to find a scientific paper on the topic, I lazily asked the All-Knowing LLM about it. And it was actually somewhat reassuring. It seems Linepithema may be suffering from imperial overreach... 

Is it true that most Argentine ants in the whole world belong to the same super-colony, or is this an over-simplification?

Yes, it’s basically true—but with important caveats.

🐜 The Claim:

Most Argentine ants (Linepithema humile) outside their native range belong to a single, vast "supercolony" in terms of genetic relatedness and behavioral cooperation—sometimes described as the largest cooperative unit in the animal kingdom.

✅ What's True:

1. Global Spread from a Single Origin:

   • Argentine ants are native to South America (mainly around northern Argentina, Uruguay, and southern Brazil).

   • When introduced abroad (via human trade in the 19th century), they underwent a genetic bottleneck—reducing their genetic diversity.

   • Invasive populations in North America, Europe, Japan, Australia, etc., are genetically similar and often do not fight each other, even across vast distances.

2. Lack of Intra-Colony Aggression:

   • In their native range, different nests often fight fiercely.

   • In invaded regions, ants from distant nests (e.g., San Diego and San Francisco) accept each other as nestmates.

   • This has led scientists to refer to these populations as a “supercolony.”

3. The "Main" Supercolony:

   • One especially well-studied group—called the "Californian supercolony"—is genetically indistinguishable from populations in Europe and Japan.

   • These ants do not recognize each other as foreign and cooperate across continents (in lab tests), suggesting a shared ancestry and compatible chemical cues.

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❗But Here's the Nuance:

1. Not All Argentine Ants Belong to One Supercolony:

   • Other distinct supercolonies exist, even within the same geographic area (e.g., in Europe and California).

   • These do fight each other—so the idea of one global ant empire is an oversimplification.

   • Even within a country, there can be multiple rival supercolonies with clear boundaries.

2. "Supercolony" is a Behavioral Category:

   • It's not a taxonomic or ecological term, but a way to describe highly cooperative, genetically similar nests.

   • Cooperation doesn’t mean coordination like bees—these are massive, decentralized networks of nests and foragers that tolerate each other.

3. Evolutionary Fragility:

   • Because of low genetic diversity, invasive Argentine ants are vulnerable to disease or environmental change.

   • Their success is tied to human-disturbed environments; they may not remain dominant in the long term.

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🧬 Summary

• ✅ True: Many Argentine ants outside their native range are genetically similar and form cooperative supercolonies, with no aggression across huge distances.

• ⚠️ Oversimplified: There is not just one single supercolony globally—there are several, and they can compete.

• 🧠 Cool fact: Ants from the California and European supercolonies recognize each other as friendly despite being 8,000+ km apart.

Would you like a diagram or map showing where the major Argentine ant supercolonies are located?